JP2002326984A - Method for producing fullerene derivative - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fullerene derivative hardly hydrolyzable and having good proton conductivity. SOLUTION: This method for producing the fullerene derivative comprises steps of reacting fullerene molecules with a hydrogensulfite and producing the fullerene derivative in which at least a sulfonic acid group is directly bound to the carbon atom constituting the fullerene molecules.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a fullerene derivative.

[0002]

2. Description of the Related Art Fullerene molecules C ₆₀ and C ₇₀ shown in FIGS. 14A and 14B were discovered in 1985 in a mass spectrometry spectrum of a cluster beam obtained by laser ablation of carbon (Kroto, HW; Heath, JR; O'Brien,
SC; Curl, RF; Smalley, RENature 1985. 318, 16
2.), and five years later, in 1990, a method of manufacturing a carbon electrode by an arc discharge method was found. Since then, fullerene molecules have attracted attention as carbon-based semiconductor materials and the like.

Further, as shown in FIG. 15, a fullerene hydroxide (commonly called “fullerenol”) is a compound having a structure in which a plurality of hydroxyl groups are added to carbon atoms constituting a fullerene molecule. (Hereinafter referred to as fullerenol)) was first reported by Chiang et al. In 1992 (Chiang, LY; Swirczew).
ski, JW; Hsu, CS; Chowdhury, SK; Cameron, S.; Creega
. n, KJChem.Soc, Commun 1992, 1791 and Chiang, LY; W
ang, LY; Swirczewski, JW; Soled, S.; Cameron, SJOr
g. Chem. 1994, 57 , 3960). Since then, fullerenol having a certain amount or more of hydroxyl groups introduced therein has been particularly noted for its water-soluble property, and has been studied mainly in the bio-related technical field.

Further, as shown in FIG. 16, a fullerenol bisulfate esterified in 1994, which is a compound in which the hydroxyl group of the above fullerenol is replaced with an OSO ₃ H group, was obtained in 1994.
Chiang et al. (Chiang, LY; Wang, LY;
Swirczewski, JW; Soled, S .; Cameron, SJOrg. Chem. 199
4, 59 , 3960).

[0005] Figure 17, by conventionally known production method, a reaction formula for synthesizing fullerenols or hydrogensulfate esterified fullerenol fullerene molecule, obtained by reaction of a fullerene molecule (e.g., C ₆₀₎ and fuming sulfuric acid reaction By introducing the product into anhydrous diethyl ether, first, a cyclosulfonated fullerene is obtained, and by hydrolyzing it, fullerenol or fullerenol hydrogensulfate can be obtained.

In recent years, for example, as a polymer solid electrolyte type fuel cell for driving an automobile, a proton (hydrogen ion) conductive polymer such as a perfluorosulfonic acid resin (such as Nafion (R) manufactured by Du Pont) has been used. Those using materials are known.

Further, relatively new as the proton _{conductor, H 3 Mo 12 PO 40 ·} 29H 2 O and Sb ₂ O ₅ · 5.4H poly molybdenum acid or oxides known with many water of hydration, such as ₂ O Have been.

[0008] When these polymer materials and hydrated compounds are placed in a wet state, they exhibit high proton conductivity near normal temperature. That is, taking a perfluorosulfonic acid resin as an example,
Protons ionized from the sulfonic acid group combine with water taken in a large amount in the polymer matrix (hydrogen bond) to produce protonated water, that is, oxonium ions (H ₃ O ⁺ ), Since protons can move smoothly in the polymer matrix in the form of oxonium ions, this kind of matrix material can exhibit a considerably high proton conduction effect even at room temperature.

On the other hand, recently, proton conductors having a completely different conduction mechanism from these have been developed. That is, Y
It has been found that a composite metal oxide having a perovskite structure, such as b-doped SrCeO ₃ , has proton conductivity without using water as a moving medium. In this composite metal oxide, it is considered that protons are independently channeled between oxygen ions forming the skeleton of the perovskite structure and are conducted.

In this case, the conductive proton does not necessarily exist in the composite metal oxide from the beginning. When the perovskite structure comes into contact with water vapor contained in the surrounding atmosphere gas, the high-temperature water molecules react with oxygen vacancies formed in the perovskite structure by doping, and this reaction causes protons to be produced for the first time. Is thought to occur.

[0011]

However, the following problems have been pointed out in the various proton conductors described above.

First, the matrix material such as the perfluorosulfonic acid resin needs to be continuously and sufficiently wet during use in order to maintain high proton conductivity. Therefore, a humidifier and various accompanying devices are required for the configuration of a system such as a fuel cell, and the size of the device is increased, and the cost of system construction is unavoidable.

Further, the operating temperature is not wide enough to prevent freezing and boiling of the water contained in the matrix.

In the case of the composite metal oxide having a perovskite structure, the operating temperature must be maintained at a high temperature of 500 ° C. or more in order to conduct meaningful proton conduction.

As described above, the conventional proton conductor has a problem that it is highly dependent on the atmosphere, such as replenishing moisture and needing steam, and the operating temperature is too high or its range is narrow. Was.

The present applicant has found that the above fullerenol and hydrogen sulfate esterified fullerenol exhibit proton conductivity, and disclosed a novel proton conductor in Japanese Patent Application Nos. 11-204038 and 2000-058116. (Hereinafter referred to as the prior invention).
The proton conductor according to the prior application can be used in a wide temperature range including room temperature, its minimum temperature is not particularly high, and it does not require moisture as a moving medium. It is. It has also been found that when the hydroxyl group is replaced with an OSO ₃ H group, the conductivity in the pellet tends to increase. This is because hydrogenation of an OSO ₃ H group is more likely to occur than a hydroxyl group.

[0017]

However, for the purpose of improving proton conductivity, the present inventors have focused on the fact that the number of sulfonic acid groups per unit mass is large, and have studied diligently with hydrogen sulfate esterified fullerenol. As a result, the hydrogen sulfate esterified fullerenol has a problem that the half ester structure of sulfuric acid is easily hydrolyzed with time, and the sulfonic acid group is eliminated.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing a fullerene derivative which is hardly hydrolyzed and has good proton conductivity. is there.

[0019]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and found that FIG.
And a compound having a structure in which a sulfonic acid group is directly bonded to a fullerene skeleton, as shown in FIG. 19, hardly hydrolyzes, shows good water and heat resistance, and has good proton conductivity. A method for producing the fullerene derivative has been reached.

FIG. 20 shows the stability of the sulfonic acid group. It can be seen from FIG. 20 that the compound having a structure in which a sulfonic acid group is directly introduced into saturated carbon is particularly stable.

That is, the present invention comprises a step of reacting a fullerene molecule with a bisulfite in the presence of oxygen to produce a fullerene derivative in which at least a sulfonic acid group is directly bonded to a carbon atom constituting the fullerene molecule. And a method for producing a fullerene derivative.

According to the production method of the present invention, a fullerene derivative in which at least a sulfonic acid group is directly bonded to a carbon atom constituting the fullerene molecule can be produced. The fullerene derivative is thermally stable because the sulfonic acid group is directly bonded to a carbon atom constituting the fullerene molecule, and does not hydrolyze in hot water, for example, and has good water resistance and heat resistance. Show.

Further, when the produced fullerene derivative is applied as a proton conductor to various electrochemical devices, for example, a fuel cell, excellent proton conductivity is exhibited.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically based on embodiments.

As shown in FIG. 1, a method for producing a fullerene derivative according to the present invention comprises adding a dimethylformamide to a mixed solution of the fullerene molecule and the bisulfite in air or oxygen gas, and adding a carash reaction ( Kharash Re
action).

As a result, it is possible to produce the fullerene derivative in which at least a sulfonic acid group is directly bonded to a carbon atom constituting the fullerene molecule.
Since it is bonded to a carbon atom constituting the fullerene molecule, it is thermally stable and does not hydrolyze even in hot water, for example. Further, it is stable even when heated to 100 ° C. or more in a high boiling point solvent such as dimethylformamide, and shows better water resistance and heat resistance.

Furthermore, when the obtained fullerene derivative is applied as a proton conductor to various electrochemical devices, for example, a fuel cell, more excellent proton conductivity can be exhibited.

FIG. 2 shows a reaction scheme of the above-mentioned Kalash reaction when, for example, an unsaturated compound is used as a raw material.

First, hydrogen sulfite ions are converted into sulfite ion radicals by oxygen. When this sulfite ion radical is reacted with the unsaturated compound [a], a compound [b] is produced. By this compound [b] and hydrogen,
Compound [c] is produced. At the same time, compound [b]
Hydrogen is eliminated to produce a compound [d]. In addition, the compound [b] reacts with the oxygen to produce a compound [e], which reacts with bisulfite ion to produce a compound [f].

The present inventors apply this Karash reaction to a reaction using the fullerene molecule as a raw material to produce the fullerene derivative in which at least a sulfonic acid group is directly bonded to a carbon atom constituting the fullerene molecule. I found that.

Examples of the bisulfite include sodium bisulfite and potassium bisulfite.

FIG. 3 shows the method for producing a fullerene derivative according to the present invention more specifically.

As shown in FIG. 3, the fullerene molecule (for example, C ₆₀ ) is reacted with, for example, sodium bisulfite as the bisulfite in the dimethylformamide at 120 ° C. for 3 days in the air. Is preferred. The disappearance of the fullerene molecules was monitored by TLC (Thin Layer Chromatography), and when the fullerene molecules disappeared, the mixed solution was poured into ether to precipitate a crude product and the sodium bisulfite, followed by filtration. To remove dimethylformamide.

Next, the above-mentioned filtration was carried out with ethanol.
From the filtrate obtained from the above,
Extract the allene derivative. The extracted product is filtered and
And dehydration to remove the ethanol, and further with NaOH
Sulfonic acid salt (-SO _ThreeNa) type and SE
Small molecules using C (Sieve Exclusion Chromatography)
Remove inorganic salts. And, the low molecular weight inorganic salt is removed.
Solvent (water) is removed by dehydrating the removed material
Then, for example, as shown in FIG.
A brown solid can be obtained as a body.

In the method for producing a fullerene derivative according to the present invention, as shown in FIG. 18, only the sulfonic acid group is replaced with a proton (H) at a carbon atom constituting the fullerene molecule.
⁺ ) The sulfonic acid group and the hydroxyl group are directly bonded to the fullerene derivative directly bonded as a dissociable group and / or the carbon atom constituting the fullerene molecule as shown in FIG. Fullerene derivatives can be produced. Here, the “proton dissociable group” means a functional group from which a proton can be eliminated by ionization, and “dissociation of proton (H ⁺ )” means that a proton is separated from a functional group by ionization. means. Further, the fullerene derivative can be further derived into a derivative having another group capable of proton dissociation.

These fullerene derivatives are thermally stable because at least the sulfonic acid group is directly bonded to the carbon atom constituting the fullerene molecule.
For example, it does not hydrolyze even in hot water. Further, it is stable even when heated to 100 ° C. or more in a high boiling point solvent such as dimethylformamide, and shows good water resistance and heat resistance.

Furthermore, when this fullerene derivative is applied as a proton conductor to various electrochemical devices, for example, a fuel cell, more excellent proton conductivity can be exhibited.

In the present invention, the introduction of a proton dissociable group
The fullerene molecule as the target parent
There is no particular limitation as long as it is a star molecule.₃₆, C
₆₀(See FIG. 14A), C₇₀(See FIG. 14B),
C₇₆, C₇₈, C₈₀, C₈₂, C ₈₄Fuller selected from etc.
A single element of a len molecule or a mixture of two or more of these
It is preferably used.

The fullerene derivative obtained according to the present invention can be suitably used as a proton conductor in various electrochemical devices such as a fuel cell.

The mechanism of proton conduction in the fuel cell is as shown in the schematic diagram of FIG.
Dissociated protons (H ⁺ ) sandwiched between an electrode (eg, a hydrogen electrode) 2 and a second electrode (eg, an oxygen electrode) 3 move from the first electrode 2 side to the second electrode 3 side in the direction of the arrow in the drawing. And move.

FIG. 5 shows a specific example of a fuel cell using the fullerene derivative obtained according to the present invention as a proton conductor. This fuel cell comprises catalysts 2a and 3
a, a negative electrode (fuel electrode or hydrogen electrode) 2 and a positive electrode (oxygen electrode) 3 with terminals 8 and 9 facing each other and closely contacting or dispersing a, and the proton conducting portion 1 is sandwiched between these two electrodes. Have been.

In use, on the negative electrode 2 side, hydrogen is supplied from the inlet 12 and discharged from the outlet 13 (which may not be provided). Protons are generated while the fuel (H ₂ ) 14 passes through the flow path 15, and the protons move toward the positive electrode 3 together with the protons generated in the proton conducting portion 1, where they are supplied from the inlet 16 to the flow path 17. Reacts with oxygen (or air) 19 toward the exhaust port 18, thereby extracting a desired electromotive force.

The fuel cell having such a structure is characterized in that protons supplied from the negative electrode 2 move to the positive electrode 3 while the protons are dissociated in the proton conducting portion 1, so that the proton conductivity is high. Therefore, since a humidifying device or the like is not required, the system can be simplified and reduced in weight.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

<Synthesis of fullerene polysulfonic acid> A fullerene molecule C ₆₀ (500 mg) and sodium bisulfite ( ₆₀ eq) were converted into dimethylformamide D in the atmosphere.
The reaction was performed at 120 ° C. for 3 days in MF (300 ml).
The disappearance of the fullerene molecules was monitored by TLC (Thin Layer Chromatography). When the fullerene molecules disappeared, the mixed solution was poured into ether (700 ml) to precipitate the crude product and the sodium bisulfite. And filtered to remove dimethylformamide.

Next, the fullerene derivative as a target product was extracted from the filtrate obtained by the filtration with ethanol (500 ml). The extracted product is filtered and dehydrated to remove the ethanol, further neutralized with NaOH, converted to a sulfonate (—SO ₃ Na) form, and subjected to SEC (Sieve Exclusion Chromatography:
Low molecular weight inorganic salts were removed using Sephadex LH-20). Then, the solvent (water) is removed by dehydrating the material from which the low-molecular-weight inorganic salt has been removed, and 507 mg of a red-black solid soluble in ethanol as the fullerene derivative as the target product (estimated structure m = 4, n
= 8 and a yield of 39%).

This fullerene derivative is treated with U in ethanol.
As a result of V-Vis measurement, a peak was observed at around 220 nm.
Shows a spectrum with a tail up to 600 nm
Was. IR spectrum (KBr) is characterized by sulfonic acid groups
1210, 1040cm ^-1Showed an absorption peak.
The MS spectrum (positive) is C₆₀Peak of
(Products decomposed during ionization) and high molecular weight
Multiple peaks on the side, the formation of adducts of sulfonic acid groups
The result was shown.

Hereinafter, the IR spectrum, ¹ H, ¹³ C-NM
Details of evaluation results such as R, XPS (X-ray electron spectroscopy), elemental analysis, etc. are shown. From these comprehensive analysis, it is found that the obtained substance has a polysulfonic acid structure as shown in FIG. It became clear. As for the reaction mechanisms of fullerene C ₆₀ and sodium bisulfite, in the completely free conditions oxygen from the reaction did not proceed, considered the Caras (Kharash) at a reaction is proceeding.

[0049] The aqueous solution of the product obtained in the reaction of <ion exchange> C ₆₀ and NaHSO _3, Amberlite-1
SV4 (solvent flow rate is 400 ml)
/ 1 hr), a fraction showing strong acidity (pH <1) was obtained. In addition, XPS analysis described later revealed that this solution did not contain sodium, and that ion exchange was completely performed under these conditions.

<IR> FIG. 6 shows an IR spectrum of the fullerene derivative obtained by the method for producing a fullerene derivative of the present invention. 1200, 34 after ion exchange
Although the peak shape around 00 cm ^-1 slightly changed, the same pattern was shown for the salt type and the acid type as a whole, and it was found that there was no significant structural change. 3430 cm ^-1 (vs, b
r), 1650 cm ^-1 (vs), 1210 cm ^-1 (v
s), 1040 cm ^-1 (vs), 880, 850 cm ^-1
(S), 650, 590 cm ^-1 (s)

< ¹ H, ¹³ C-NMR (DMSO-d ₀ )>
As shown in FIG. 7A, the result of ¹ H-NMR was 9.9.
8, 8.17, 4.4 (br) and 2.9 (br) pp
m, a signal was observed for each of the sulfonic acid groups (SO
₃ H), DMF aldehyde group, OH group and a methyl group (methylene group) is considered to be derived from.

Further, as shown in FIG. 7B, the result of ¹³ C-NMR was that a broad peak derived from a fullerene skeleton was observed at around 148 ppm. Further, a broad peak derived from -CO- (or -CN, -CS-) was observed around 57 ppm, and the other peak was 164 ppm.
A signal derived from ＯO and a sharp peak at around 35 ppm are observed. These results are considered to be derived from DMF added to the fullerene molecule from the results of the following elemental analysis.

<XPS Analysis> The results of the XPS analysis are shown in FIG. According to this XPS elemental analysis, Na was not detected. In the analysis of the C1s peak, C—C or C—H, 69; C—O, C—S or C—N, 19;
O, 4; COO, 5; π-π, 4 (%). S2
In p peak analysis, CS or SS, 3;
^₂ -, 26; -SO ₄ ^2- or -SO ₃ ^-, 71 (%), and the presence of C-S bond was confirmed.

<Elemental analysis (combustion method)> The results of the elemental analysis are shown in FIG. As shown in FIG. 9, C = 48.51, H =
3.35, N = 3.82, S = 14.06, (O) = 3
0.26 (%). In addition, NMR and X
From the results of PS, assuming a structure in which a sulfonic acid group and a hydroxyl group and DMF were several added to the fullerene C _60, C
₆₀ (SO ₃ H) _n (OH) _n (CH ₂ N (CHO) CH ₃ ) _m
When the weight percentage of each element in the case of is calculated, m = 4 CHNSO (%) n = 65.14 2.27 3.51 12.04 28.04 n = 7 51.00 2.26 3. 30 13.24 30.20 n = 8 48.22 2.25 3.12 14.30 32.11 It can be determined that adducts with n = 7 to 8 were obtained on average.

<Proton Conductivity> The proton conductivity at room temperature (20 ° C.) determined by the AC impedance method is about 2 × 10 ⁻³ Scm ^−1, which is a good value.
As shown in FIG. 0, the fullerene derivatives obtained according to the present invention exhibit excellent proton conductivity even at high temperatures. In the figure, data of Nafion (manufactured by DuPont) is also shown for comparison.

<Water Resistance / Heat Stability> Even after the fullerene derivative obtained according to the present invention was stirred in hot water (85 ° C.) for 10 hours, no phenomenon such as sedimentation was visually observed. As is clear from FIG. 11 showing the result of the FT-IR measurement after the stirring treatment and the compound separation in hot water and FIG. 6 showing the result of the FT-IR measurement before the stirring treatment, the sulfonic acid group was retained. No change was observed. Similarly, a fullerene sulfate having a similar structure is stirred in hot water, and the F before and after the stirring (FIG. 13) is processed.
Comparing the T-IR measurement results, it is found that the treatment completely hydrolyzed, the sulfonic acid group was eliminated and converted to polyhydroxy fullerene.

[0057]

According to the production method of the present invention, a fullerene derivative in which at least a sulfonic acid group is directly bonded to a carbon atom constituting the fullerene molecule can be produced. Since the sulfonic acid group is directly bonded to the carbon atom constituting the fullerene molecule, it is thermally stable and exhibits good water resistance and heat resistance without hydrolyzing even in hot water.

Further, when the produced fullerene derivative is applied as a proton conductor to various electrochemical devices such as a fuel cell, excellent proton conductivity is exhibited.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for producing a fullerene derivative according to the present invention.

FIG. 2 is a reaction structural formula showing a Kalash reaction.

FIG. 3 is a diagram showing a method for producing a fullerene derivative according to the present invention.

FIG. 4 is a schematic view showing an example in which a fullerene derivative obtained according to the present invention is used as a proton conductor.

FIG. 5 is a schematic sectional view of a fuel cell according to an embodiment using a fullerene derivative obtained according to the present invention as a proton conductor.

FIG. 6 is a view showing an IR spectrum of a fullerene derivative obtained according to the present invention.

FIG. 7 is a diagram showing an NMR spectrum of a fullerene derivative obtained according to the present invention.

FIG. 8 is a view showing a measurement result of an XPS analysis of a fullerene derivative obtained according to the present invention.

FIG. 9 is a diagram showing an elemental analysis result of a fullerene derivative obtained according to the present invention.

FIG. 10 is a diagram showing a measurement result of a fullerene derivative obtained based on the present invention by an AC impedance method.

FIG. 11 is a view showing an IR spectrum of a fullerene derivative obtained according to the present invention after stirring in hot water.

FIG. 12 is a view showing an IR spectrum of polyhydroxylated fullerene sulfate.

FIG. 13 is a view showing an IR spectrum of polyhydroxyfullerene sulfate in hot water after stirring.

FIG. 14 is a structural diagram of a fullerene molecule.

FIG. 15 is a structural diagram of a polyhydroxylated fullerene.

FIG. 16 is a structural view of hydrolyzed poly (hydroxy fullerene hydrogen sulfate).

FIG. 17 is a reaction scheme showing a conventionally known synthesis method for synthesizing a hydrolyzed poly (hydroxy fullerene hydrogen sulfate).

FIG. 18 is a structural diagram of a fullerene derivative obtained according to the present invention without hydrolysis.

FIG. 19 is a structural diagram of another fullerene derivative obtained according to the present invention without hydrolysis.

FIG. 20 is a diagram showing the stability of a sulfonic acid group.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Proton conduction part, 2 ... 1st electrode (hydrogen electrode), 2a ... catalyst, 3 ... 2nd electrode (oxygen electrode), 3a ... catalyst, 14 ... hydrogen,
19 ... oxygen (or air)

Claims (6)

[Claims] 1. A method for producing a fullerene derivative, comprising: reacting a fullerene molecule with a bisulfite in the presence of oxygen to produce a fullerene derivative in which at least a sulfonic acid group is directly bonded to a carbon atom constituting the fullerene molecule. Production method. 2. The method for producing a fullerene derivative according to claim 1, wherein dimethylformamide is added to a mixed solution of the fullerene molecule and the bisulfite in air or oxygen gas to cause a Karash reaction. . 3. The method for producing a fullerene derivative according to claim 1, wherein the bisulfite is sodium bisulfite or potassium bisulfite. 4. The production of a fullerene derivative according to claim 1, wherein the sulfonic acid group and / or the hydroxyl group is directly bonded to a carbon atom constituting the fullerene molecule as a proton-dissociable group. Method. 5. The method for producing a fullerene derivative according to claim 4, wherein the group is further derived to another group capable of proton dissociation. 6. The spherical carbon cluster molecule C _m (m = 36, 60, 70, 76, 7) as the fullerene molecule
8, 80, 82, 84) using the fullerene derivative according to claim 1.